Look for Khronos OpenGL spec files using pkg-config, rather than downloading them
Also add a --with-khronos-spec-dir=PATH configure option so XWin can be directed
where to find these files without using the khronos-spec-files package
XWin with AIGLX requires OpenGL spec files in order to generate wrapper code which:
(1) thunks from the glapi dispatch table which uses the default cdecl calling convention
to native GL functions using the stdcall calling convention.
(2) performs function address lookup for OpenGL 1.2+ functions, which are treated
as extensions and so not directly linkable.
v2: KHRONOS_SPEC_DIR is only valid when XWIN_GLX_WINDOWS is defined. Avoid 'make dist'
seeing invalid dependencies by only including rules using KHRONOS_SPEC_DIR if
XWIN_GLX_WINDOWS is defined
Signed-off-by: Jon TURNEY <jon.turney@dronecode.org.uk>
Reviewed-by: Colin Harrison <colin.harrison@virgin.net>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
a50878682c